Effects of microstructure and specimen thickness on the fatigue crack closure in Al-Li 8090 alloy
- Pohang Univ. of Science and Technology (Korea, Republic of). Center for Advanced Aerospace Materials
- Agency for Defense Development, Yuseong (Korea, Republic of)
The effect of specimen thickness on the crack closure and fatigue crack propagation has been investigated in this study using an Al-Li 8090 alloy. Since the crack closure is largely affected by the microstructural variation, the closure loads are measured and compared in two different microstructures, viz., one having a planar slip mode and the other with a homogeneous slip mode. The alloy used in the present study was an Al-Li 8090 alloy with the nominal composition of Al-2.5Li-1.2Cu-0.9Mg-0.11Zr. The plate was received in the T3771 tempered condition, which was solution treated, 6% stretched and naturally aged. The as-received microstructure showed a typical pancake-shaped unrecrystallized grain structure along the rolling direction. To obtain the microstructures with different slip characteristics, two types of heat treatment were used to vary the S{prime} phase distribution. The microstructure showing the homogeneous slip behavior was obtained by aging the as-received material at 190 C for 16 hours, resulting in a homogeneous distribution of S{prime} phase along with {delta}{prime} phase (S{prime} + {delta}{prime} structure). The microstructure exhibiting the planar slip behavior was attained by solution treating the as-received alloy at 530 C for 30 minutes, followed by 16 hours aging at 190 C to produce a primarily {delta}{prime} phase microstructure ({delta}{prime} structure).
- OSTI ID:
- 55414
- Journal Information:
- Scripta Metallurgica et Materialia, Vol. 32, Issue 8; Other Information: PBD: 15 Apr 1995
- Country of Publication:
- United States
- Language:
- English
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